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Old 10-10-2017, 10:52 AM   #41
Jtroutt19
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Default Re: Cuisinart wine cooler P/S board problems

Success guys! Turns out them two damn resistors was what was doing it. Cooler is working perfectly now. I did upgrade those two resistors from 1/8watt to 1/4 watt.

Thanks for all the help guys.
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Old 10-10-2017, 12:43 PM   #42
momaka
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Default Re: Cuisinart wine cooler P/S board problems

Nice work!

Looks like you finally won the battle with those two resistors. With the caps ruled out, it just had to be something in the BJT drive circuit that was messing up the PSU. I just wasn't sure if the problem was on the primary or the secondary, so I couldn't give you any further guidance. But I'm glad you didn't give up and ended up repairing the PSU. A lot of times, that's all there is to troubleshooting - going back and forth and checking everything several times until the problem finally shows itself.

Cheers!
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Old 10-10-2017, 03:38 PM   #43
Jtroutt19
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Default Re: Cuisinart wine cooler P/S board problems

Thank you for the help! I am slowly learning all this. I have taken a few classes in AC and DC powers and basic circuit design. But theory is a lot different than the real deal. I would like to find some resources that would help me understand powersupplies a bit better.
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Old 10-11-2017, 01:12 PM   #44
momaka
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Default Re: Cuisinart wine cooler P/S board problems

Though a bit dated and not 100% accurate in some small parts, this IMO is usually a good starting point for understanding basic SMPS concepts:
http://www.hardwaresecrets.com/anato...ower-supplies/

I've heard that YouTube also has some good videos / channels on SMPSes, though I'm not sure which. Hopefully someone else can chime in on that.

Knowledge in the following areas would also be extremely helpful to you: resistor divider circuits, rectifier circuits, passive filters (LC/RLC), transistor circuits (switching and linear), op-amps, and finally buck-boost (for understanding APFC).

I started by tracing out cheap half-bridge power supplies like the one in this thread and later single-transistor forward (STF) PSUs. Both are fairly simple to understand and repair. So once you understand those, the rest won't be that much harder. I still struggle with understanding some of the discrete protection circuits and compensation circuits, but that's only a small portion of SMPSes that doesn't usually go bad or cause any problems. Most of your focus should be on the large power components and their driver circuits.

In the case of your PSU above, the two 10 Ohm resistors that were bad were part of the BJT drive circuit on the primary side - that's probably why those transistors could not switch properly and you got voltage sagging past a certain load.

Last edited by momaka; 10-11-2017 at 01:13 PM..
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